The present invention relates to a self-propelled endoscope apparatus for performing endoscopic procedures in which many of the hazards posed by conventional endoscopes are eliminated.
Within this application several publications are referenced by arabic numerals within parentheses. Full citations for these and other references may be found at the end of the specification immediately preceding the claims. The disclosures of all of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.
One of the major applications of gastrointestinal endoscopy is the detection of pre-malignant and malignant lesions of the gastrointestinal tract. There are approximately 250,000 new cases of colon cancer diagnosed in the United States every year. Approximately 50,000 of these people die of colon cancer every year. Colon cancer represents the number one killing cancer affecting both sexes nearly equally (breast cancer is much more common in women than in men). Not only in the United States, but in Western societies in general, colon cancer is a major health problem (1).
Despite the lethality of colon cancer, there exists an opportunity for its prevention by detecting and removing the precursor of the actual cancer. This precursor lesion is the polyp. This is a small (generally less than 1 cm diameter) growth on the lining of the bowel. It represents an area of the lining of the bowel which has undergone neoplastic transformation--i.e. clones of the cells which have undergone a genetic change enabling them to escape the regulatory systems controlling normal cell growth. While a polyp is neoplastic, it is still benign, since it is not capable of invading other structures or of metastasizing to other locations.
Endoscopic technology permits the detection and removal of polyps from the gastrointestinal tract without resorting to major invasive surgery. When polyps are endoscopically removed, they generally do not recur. However, if polyps are not removed, some of them will undergo malignant transformation and become cancers. A cancer is capable of infiltrating its cells into normal tissues, and is also capable of metastasizing. Unlike polyps, a cancer will recur unless a fairly radical operation is done. Unfortunately, the overall cure rate for colon cancers is less than 50% even if extensive surgery is done.
Theoretically, if one could detect and remove all colon polyps, the incidence of colon cancer would be very low (there are probably some cancers that arise de novo, without a preceding benign polyp precursor) (2). Flexible endoscopes (e.g. colonoscopes) make this possible.
Conventional endoscopes are constructed as follows: there is a long flexible shaft, with a diameter suitable to the organ for which it is intended. A flexible colonoscope is about 14 mm in diameter and 180 cm in length. The shaft is encased with a metallic double helical spiral that resists torsional deformation while permitting axial flexibility. The distal 8 cm of the endoscope, the bending section, is a stacked series of universal joints. Wires operated by controls at the proximal end of the endoscope cause the bending section to bend in whatever direction is desired. The shaft also contains fiberoptic bundles to bring light to the scene at the tip of the endoscope. A video chip with appropriate optics and video electronics is mounted at the tip of the endoscope and the image is conveyed by wires back to the operator. The shaft of the endoscope also incorporates small tubes to bring air and water into the field. The air is used to open up the bowel to obtain a clear view. The water is used to clean the endoscope's optics. The shaft also contains a channel to pass instruments such as biopsy forceps or snares to remove polyps.
Essentially, the operator of the endoscope pushes it into the bowel. The scope is of necessity flexible so that it can fit around the curvatures of the bowel. The bowel itself is not only curved but also is capable of stretching or being looped into curves which are exaggerations of the normal anatomic position. Therefore, as the endoscope is pushed into the bowel, it stretches the bowel. When the bowel is forced into these stretched loops by the insertion of the endoscope, the patient is made uncomfortable. If the doctor does not recognize that the bowel is being unduly stretched, the bowel wall will tear and a perforation occurs, requiring an emergency operation to repair (3). A skilled operator of the endoscope can avoid excessive stretching or looping, but even a skilled operator cannot avoid causing some discomfort to the patient and very occasionally even serious harmful effects. Manipulating the shaft of the endoscope so that excessive looping does not occur is a blind process. The operator is aware by direct endoscopic vision of what lies ahead of the endoscope, but he is only indirectly aware of how the shaft is interacting with the bowel to form loops. Thus, even a skilled operator may not be aware of the formation of an excessive loop and a serious complication may ensue (4).
Additionally, a conventional endoscope cannot be sterilized in the same way as a simple stainless steel surgical instrument. This lack of absolute sterilizability results from the conventional endoscope's complex hybrid construction of metallic parts, plastic parts, electronics and optics which would be destroyed by the high temperatures used in steam autoclaves. These instruments can be sterilized by use of an ethylene oxide gas process ("gas sterilization"), but this procedure requires approximately six to eight hours. Since endoscopes are expensive, it is not practical to have enough endoscopes in reserve to do all the procedures that one might do in one day. Therefore, what is conventionally done is "cold soaking", which refers to the use of a bactericidal/viricidal liquid such as glutaraldehyde to achieve a high degree of disinfection. This process takes about a half hour to perform, which is compatible with the turn-over requirements of an endoscopy unit. However, a high level of disinfection is not the same as absolute sterilization by autoclave. In addition, the actual ability of the glutaraldehyde to achieve high disinfection is dependent on diligent pre-cleaning of mucus and other substances from the numerous channels and crevices which exist in the endoscope. If this tenacious debris is not removed, the glutaraldehyde will not be able to penetrate to achieve killing of micro-organisms (5,6).